This project includes a series of studies designed to describe the development of sleep/wake patterns in adolescents, factors that affect adolescent sleep patterns, vulnerabilities that arise from poor sleep patterns, and measures that may improve sleep hygiene and quality of life in adolescents. A variety of approaches is used to accomplish these goals. Study 1 is a 5-year longitudinal survey of sleep habits, daytime sleepiness, circadian type, and depressive mood. Surveys are performed twice annually (fall/ spring) in three cohorts (approximately 500 each) of school children beginning in grades 5, 8, and 11. Teachers are also asked to rate these students on social maturity, physical maturity, and academic progress. The surveys provide descriptive data spanning adolescence. Data are also analyzed to determine relationships among variables. For example, do sleep/wake patterns predict academic progress? Study 2 includes three protocols to examine several factors in greater detail. The first protocol assesses the extent to which a student's circadian type influences adjustment to a school schedule alteration. Morning and evening type students in 6th and 8th grades are evaluated across the transition to the next grade, which involves an earlier school day. Measures include sleep diaries and wrist actigraphy three times (spring, summer, fall) for two consecutive weeks. Classroom Multiple Sleep Latency Tests (MSLTs) are performed during spring and fall evaluations. This study tests the hypothesis that evening types have greater difficulty adjusting to an earlier school day, as evidenced by disturbed sleep, daytime sleepiness, and negative mood. The second protocol examines relationships among puberty, sleep, and waking vulnerabilities in 5th through 8th grade students. Sleep diaries, actigraphy, and classroom MSLTs are used to evaluate the impact of pre/early versus late pubertal stage on need for sleep and level of daytime functioning in adolescents. The third protocol uses sleep diaries, actigraphy, and classroom MSLTs to determine whether employment affects sleep/wake patterns negatively. The following groups of high school juniors and seniors are evaluated: students working 25-35 hours per week, 5-15 hours per week, and <5 hours per week (plus athletics), half of whom have work or work-outs on >3 school mornings each week. Study 3 examines whether sleep hygiene training for sixth graders has a positive impact on their sleep/wake patterns. Students are assessed before and three times (6, 12, and 18 months) after a program of instruction. Sleep patterns and waking vulnerabilities are compared across time and also with a control group of students who receive training in social skills. Study 4 examines efficacy of treatment using phase delay or phase advance in adolescents with chronic oversleeping/delayed sleep phase syndrome.